Metabolic Studies in Cattle using the Hyperinsulinemic Euglycemic Clamp Technique

Sternbauer, K. 2005. Metabolic studies in cattle using the hyperinsulinemic euglycemic clamp technique. Doctoral dissertation. ISSN 1652-6880, ISBN 91-576-7037-4. Hyperinsulinemic euglycemic clamp, HEC, originally developed for determing insulinmediated glucose disposal and insulin sensitivity in humans, was used and evaluated in cattle. In the present study the following investigations were performed: the bovine physiological responses during drug-induced insulin resistance, the influence of liberal or restricted concentrate feeding on insulin sensitivity, the impact of two different physical activity levels on insulin sensitivity and muscle characteristics, and finally the expression of abomasal efflux rates in relation to different blood glucose levels. Clenbuterol and flumethasone treatment induced insulin resistance in calves lasting less than 17 hrs and 3 days post-treatment, respectively. The effect of flumethasone was more manifest than that of clenbuterol. Insulin sensitivity and muscle characteristics did not differ between one group of calves exposed to light exercise and another group of calves not exercised for 4 to 5 weeks. The results indicated that growth may have an influence on insulin sensitivity. The blood glucose levels of heifers fed concentrate at the upper limit, according to Swedish feeding standards, were higher than in heifers fed quantities at the lower limit. There was no change in insulin sensitivity or insulin levels between the two groups. A high plasma glucose level was shown to reduce the abomasal efflux rate and increase the abomasal pH in non-pregnant, non-lactating cows. The results show that the HEC technique may be a useful means for investigating druginduced insulin resistance and can also be used to create specific experimental conditions. Ruminant gluconeogenesis may still occur to some extent during HEC application, especially in lactating cows, and therefore this must be considered in future studies.